A down payment is a portion of available money given at the outset of a loan to demonstrate commitment to the purchase. A down payment is often given in cash, though in some cases it may be attached to an alternate line of credit. A down payment is usually only used in sales which involve a large amount of money. Loans to purchase houses and land are the most common loans to require a down payment, though loans for cars, boats and other luxury goods purchased on credit may also ask for a portion of the total cost up front.

The down payment system exists because a link has been shown between the amount of real investment a borrower has in their purchase, and their fidelity in continuing to make payments regularly until the full amount owed has been settled. A down payment acts as a sort of insurance for lenders, since borrowers know that if they default on their loan, they will lose not only the property they were purchasing, but also their down payment. The traditional down payment for a house in the United States has been 20%, an amount that is sufficient to tie most people to their loans. In recent years, however, upward-spiraling property costs have made saving up 20% difficult, if not impossible, for many families.

Various incentive programs and more complex lending solutions, which may bring the down payment needed down to nothing, now exist for first-time buyers and veteran buyers alike. The 80-20 loan arrangement is one which has become relatively popular, in which the first 80% of the loan is taken out as a first mortgage, and the remaining 20% is taken out as a second mortgage, leaving the buyer with no down payment commitment, simply less beneficial terms than they might otherwise have. Interest-only loans are another path which may allow a buyer to pay a substantially smaller down payment than 20% -- often as low as 3-6% of the total cost.

Down payment 'grants' also exist through non-profit organizations such as Nehemiah and AmeriDream. These organizations use a loophole in US housing regulations which prohibits a seller from giving money directly to a buyer, and grant the down payment to the buyer -- usually with a slightly higher final price as a trade-off. While the traditional 20% down payment seems high to many Americans, many other developed nations have much higher average down payments. Mexico has a 30% average down payment, Germany a 40% one, and Italy a full 50% of the final cost.